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SWAP Samples the Solar Wind

This figure shows an initial color-coded spectrogram produced by the Solar Wind Around Pluto (SWAP) instrument on New Horizons at about 4.9 astronomical units from the Sun (about 0.4 astronomical units, or 60 million kilometers, upstream from Jupiter). Interplanetary shocks passed over the New Horizons spacecraft on January 11 and January 14, causing the abrupt jumps in solar wind speed; the speed immediately following the latter shock was in excess of 600 kilometers per second. The slowly decreasing speed after the second shock is a rarefaction region, which forms as faster solar wind outruns the slower solar wind behind it. In all, these SWAP observations show a clear solar wind stream structure. Continuing plasma observations such as these will be critical to understanding the solar wind drivers of the Jovian magnetosphere as New Horizons approaches and recedes from Jupiter as well as directly measuring the internal plasma properties of the Jovian magnetosphere as New Horizons flies through this immense magnetic and plasma structure.